Handheld skin measuring or monitoring device

ABSTRACT

A handheld skin monitoring or measuring device includes a camera having a camera optical axis; and a structured light arrangement configured to project three or more laser fan beams such that the laser fan beams cross at a crossing point in front of the camera.

FIELD OF THE INVENTION

The invention relates to devices and methods for monitoring or measuringskin features, such as wounds, ulcers, sores, lesions, tumors, bruises,burns, psoriasis, keloids, skin cancers, erythema, cellulitis or thelike.

BACKGROUND TO THE INVENTION

Reference to any prior art in this specification does not constitute anadmission that such prior art forms part of the common generalknowledge.

Various techniques have been used to monitor wounds, ulcers, sores,lesions, tumors etc. (herein referred to collectively as “wounds”) bothwithin hospitals and outside hospitals (e.g. in domiciliary based care,primary care facilities etc.). Manual techniques are typicallylabor-intensive and require examination and contact by skilledpersonnel. Such measurements may be inaccurate and there may besignificant variation between measurements made by different personnel.Further, traditional approaches may not preserve any visual record forreview by an expert or for subsequent comparison.

A number of techniques for the automated monitoring of wounds have beenproposed; see for example U.S. Pat. No. 6,101,408, U.S. Pat. No.6,873,340, U.S. Pat. No. 4,535,782 and U.S. Pat. No. 5,967,979. A commonapproach is to place a reference object next to the wound and determinethe size of the wound utilizing the scale of the reference object. It isoften undesirable to place a reference object near to a wound and thisrequires an additional cumbersome step for a user and riskscontamination of the wound. Further, when the target is not in the planeof the wound, or if the wound is not planar, there will be errors in anyarea calculation.

Other systems, such as that described in US2004/0136579, require thecamera always to be positioned with a guide against the patient's skin.While this consistently positions the camera a desired distance from thesurface to be photographed and therefore sets the scale of the image, itis unwieldy and requires undesirable contact with the skin, riskingcontamination of the wound.

Many prior systems also suffer from high cost, which limits uptake ofthe systems.

The Applicant's prior specification published as US2009/213213 proposeda handheld surface measuring device based on a structured light device.(The contents of that specification are hereby incorporated by referenceherein.) A laser fan-beam was projected at a known angle to a cameraoptical axis and the resulting image data could be used to measure woundproperties such as area or depth. However, the Applicant has recognizedthat further improvements in wound measurement are possible.

It is an object of the invention to provide an improved device formonitoring or measuring skin features, or to at least provide the publicwith a useful choice.

SUMMARY OF THE INVENTION

The invention provides a handheld skin monitoring or measuring device,method and system. The invention relies on structured light techniquesand in some embodiments uses a structured light arrangement configuredto project three or more laser fan beams such that the laser fan beamscross at a crossing point in front of the camera.

In a first aspect the invention provides a handheld skin monitoring ormeasuring device, including: a camera having a camera optical axis; anda structured light arrangement configured to project three or more laserfan beams such that the laser fan beams cross at a crossing point infront of the camera.

Preferably the structured light arrangement is configured to project thelaser fan-beams such that a pattern formed by the laser fan-beams on askin surface varies with a distance between the device and the skinsurface, and wherein the pattern is a predetermined pattern when thedevice is at a distance from the skin surface within an optimum range,such that a user is enabled to position the handheld skin monitoring ormeasuring device at a distance from the skin surface within the optimumrange by adjusting the distance such that the predetermined laserpattern is formed on the surface.

Preferably the predetermined pattern includes the laser fan-beamscrossing at the crossing point, and a user is enabled to position thehandheld skin monitoring or measuring device at a distance from a skinsurface within an optimum range by aligning the crossing point with theskin surface.

Preferably the camera has a camera field of view and the three or morelaser fan beams subtend fan beam angles corresponding to the camerafield of view, such that the ends of the laser beams projected onto askin surface define a region that substantially corresponds to an imageframe of the camera.

Preferably the region occupies between 80% and 120% of the area of theimage frame.

Preferably the device has no display.

Preferably the device further includes a capture switch, the devicebeing arranged to capture data on actuation of the capture switch.

Preferably the device further includes a communications port, the devicebeing configured to transmit data captured by the camera from thecommunications port.

Preferably the device further includes memory configured to store datacaptured by the camera.

Preferably the device further includes one or more light sourcesconfigured to illuminate the skin surface.

Preferably the device is configured to capture at least the followingdata in response to a single user capture instruction: an image with thelaser fan beams switched off; and at least three images each includingone or more laser fan beams, such that each laser fan beam isunambiguously identifiable.

Preferably the device further includes a substantially spherical housingdimensioned to fit a user's cupped hand, the camera and structured lightarrangement being mounted in the housing.

Preferably the structured light arrangement is configured to projectthree laser fan beams from sources distributed evenly around the cameraoptical axis such that the three laser fan beams form an equilateraltriangle in any plane that is perpendicular to the camera optical axisand does not include the crossing point.

Preferably the structured light arrangement is configured to projectthree laser fan beams.

In a second aspect the invention provides a handheld skin monitoring ormeasuring device, including: a camera having a camera optical axis and acamera field of view; and a structured light arrangement configured toproject three or more laser fan beams such that the laser fan beamscross at a crossing point in front of the camera, the laser fan beamssubtending fan beam angles corresponding to the camera field of view,such that the ends of the laser beams projected onto a skin surfacedefine a region that substantially corresponds to an image frame of thecamera.

Preferably a user can position the handheld skin monitoring or measuringdevice at a distance from a skin surface within an optimum range byadjusting the distance such that a predetermined laser pattern isprojected onto the surface.

Preferably a user can position the handheld skin monitoring or measuringdevice at a distance from a skin surface within an optimum range byaligning the crossing point with the skin surface.

Preferably the region occupies between 80% and 120% of the area of theimage frame.

Preferably the device has no display.

Preferably the device further includes a capture switch, the devicebeing arranged to capture data on actuation of the capture switch.

Preferably the device further includes a communications port, the devicebeing configured to transmit data captured by the camera from thecommunications port.

Preferably the device further includes memory configured to store datacaptured by the camera.

Preferably the device further includes one or more light sourcesconfigured to illuminate the skin surface.

Preferably the device is configured to capture at least the followingdata in response to a single user capture instruction: an image with thelaser fan beams switched off; and at least three images each includingone or more laser fan beams, such that each laser fan beam can beunambiguously identified.

Preferably the device further includes a substantially spherical housingdimensioned to fit a user's cupped hand, the camera and structured lightarrangement being mounted in the housing.

Preferably the structured light arrangement is configured to projectthree laser fan beams from sources distributed evenly around the cameraoptical axis such that the three laser fan beams form an equilateraltriangle in any plane that is perpendicular to the camera optical axisand does not include the crossing point.

Preferably the structured light arrangement is configured to projectthree laser fan beams.

In a further aspect the invention provide a method of capturing dataconcerning a skin feature using a handheld skin monitoring or measuringdevice, including: a camera having a camera optical axis and a camerafield of view; a structured light arrangement configured to projectthree or more laser fan beams such that the laser fan beams cross at acrossing point in front of the camera; the laser fan beams subtendingfan beam angles corresponding to the camera field of view, such that thelaser beams projected onto a skin surface define a region thatsubstantially corresponds to an image frame of the camera; the methodincluding: directing the handheld skin monitoring or measuring devicetowards a skin surface; projecting at least some of the laser fan beamsusing the structured light arrangement; and adjusting a position of thehandheld skin monitoring or measuring device such that laser fan beamsdefine a desired image region on the skin surface; and capturing datausing the camera.

In a further aspect the invention provides a display-less handheld skinmonitoring or measuring device including: a substantially sphericalhousing dimensioned to fit the cupped hand of a user; a camera mountedin the housing; a structured light arrangement mounted in the housingand configured to project three or more laser fan beams such that thelaser fan beams cross at a crossing point in front of the camera; and acommunications link configured to transmit image data captured by thecamera.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be described by way of example only, withreference to the accompanying drawings, in which:

FIG. 1 is a perspective view of a handheld skin measuring or monitoringdevice according to one embodiment;

FIG. 1 a shows the device of FIG. 1 in the cupped hand of a user;

FIG. 2 is a second perspective view of the device of FIG. 1;

FIG. 3 is a first side view of the device of FIG. 1;

FIG. 4 is a second side view of the device of FIG. 1;

FIG. 5 is a third side view of the device of FIG. 1;

FIG. 6 is a top view of the device of FIG. 1;

FIG. 7 is a cut-away top view of the device of FIG. 1;

FIG. 8 shows the mounting of the camera and structured light accordingto one embodiment;

FIG. 9 shows a laser fan-beam projector projecting a laser fan-beam ontoa surface;

FIG. 10 shows a laser pattern projected onto a surface by the device ofFIG. 1;

FIG. 11 shows a further laser pattern projected onto a surface by thedevice of FIG. 1;

FIG. 12 shows a further laser pattern projected onto a surface by thedevice of FIG. 1;

FIG. 13 shows a laser pattern projected onto a skin surface and skinfeature by the device of FIG. 1;

FIG. 14 shows a skin monitoring and measuring system according to oneembodiment;

FIG. 15 shows a laser pattern projected onto a surface by a deviceaccording to a further embodiment;

FIG. 16 shows a skin measuring or monitoring device according to afurther embodiment;

FIG. 17 is a flow diagram illustrating a data capture sequence;

FIG. 18 shows a laser pattern projected onto a surface by a deviceaccording to yet a further embodiment; and

FIG. 19 shows a further laser pattern projected onto a surface by thedevice of the embodiment of FIG. 18; and

FIG. 20 shows a further laser pattern projected onto a surface by thedevice of the embodiment of FIG. 18.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

The invention relates to devices for monitoring or measuring skinfeatures, such as wounds, ulcers, sores, lesions, tumors, bruises,burns, psoriasis, keloids, skin cancers, erythema, cellulitis or thelike.

FIGS. 1 to 7 show a skin measuring or monitoring device 1 according toone embodiment. The device includes a housing 2 that has a generallycircular or elliptical cross-section, as shown in FIG. 6, and asubstantially spherical shape, as shown in e.g. FIGS. 1 and 2. In thisspecification “substantially spherical shape” does not exclude thepossibility of flat areas, such as the front face 6 of the device shownin the drawings, recessed areas around the camera lens etc. In theembodiment shown the substantially spherical housing 2 has a generallycurved rear surface to fit a user's hand, while the front face 6 of thedevice is flat.

The housing 2 is made to be held in the cupped hand of a user, such thatthe user's fingers extend around the sides of the housing 2 and a user'sfinger or thumb (preferably the index or middle finger) can bepositioned on capture button 4, as shown in FIG. 1 a. This shape allowsthe device 1 to be positioned with a significant degree of flexibility.This is important because the device may be used to capture images forskin features in difficult to access areas, such as the underside of animmobile patient's leg. This is also useful where there is limited spaceavailable to access the skin feature. This shape also allows convenientone-handed operation, which in turn allows the user's other hand to beused to aid positioning of an immobile patient or for any othernecessary purpose.

In one embodiment the housing 2 may have a diameter in the range around85 to 115 mm (around 3.3 to 4.5 inches), preferably around 100 mm(around 3.9 inches). In the embodiment shown this diameter is measuredtransverse to the optical axis 7 (FIG. 3). This measurement provides acomfortable fit for most hand sizes. Parallel to the optical axis thehousing 2 may measure around 70 mm (around 2.7 inches), this measurementbeing less than the diameter due to the flattened front face 6 of thedevice 1. The measurements of the housing are preferably sufficientlysmall to be comfortably held and sufficiently large that the averageuser's fingers and thumbs will not contact the optical apertures on thefront surface, in the normal holding position shown in FIG. 1A.

The device 1 includes a camera 5 (FIG. 7) that may be mounted in thehousing 2. The camera optical axis 7 extends forwards of the housing 2,as shown in FIG. 3.

The camera 5 may be mounted in fixed relation to a structured lightarrangement 8, as shown in FIG. 8. The structured light arrangement 8 isconfigured to project three laser fan beams or stripes. The structuredlight arrangement 8 may include three laser fan-beam projectors 9 evenlydistributed around the camera optical axis 7. In FIG. 8, the camera 5and structured light arrangement 8 are mounted in a rigid framework 10.The laser fan-beam projectors 9 are preferably adjustably mounted toallow factory calibration of the structured light arrangement. Forexample, the laser fan-beam projectors 9 may be mounted using set-screwsallowing small adjustments in the laser fan-beams.

FIG. 7 is a front view of the device 1 with the framework 10 omitted.The device may also include a transparent window, such that the cameraand/or structured light arrangement is positioned behind the window.This figure shows the structured light projectors 9 and camera 5. Inaddition this figure shows a number of light sources 11. These lightsources 11 may be used to illuminate the skin surface during some imagecapture steps, as will be described further below. These may be anysuitable diffuse light sources for illumination of a skin surface. Inone embodiment white light emitting diodes (LEDs) may be used.

A laser fan-beam emitted by a single laser fan-beam projector 9 is shownin FIG. 9. The laser fan-beam projector 9 is directed towards a surfaceS. The projected laser beam has a fan-beam angle ∝ and is relativelythin, such that a laser line 12 is projected onto a flat surface S. Theshape of the fan-beam on a non-flat surface will be more complex, aswill be discussed further below. The length of the laser fan-beam line12 will depend on the fan-beam angle ∝, the distance between the laserfan-beam projector 9 and the surface S, and the relative angle betweenthe laser fan-beam projector 9 and the surface S.

The laser fan-beam angle ∝ may be adjusted using an adjustable mask. Forexample, a small set screw may be positioned at each side of theprojector 9. Adjustment of the two set-screws allows the fan-beam angleto be narrowed or broadened in the factory at the time of manufacturingor assembly.

The three laser fan-beams are arranged at an angle towards the opticalaxis. As shown in FIGS. 7 and 8 the laser fan-beam projectors 9 aremounted at a distance from the optical axis. This means that the threefan-beams will cross at a crossing point in front of the camera. Thispoint may be on the optical axis. However, this will depend on thealignment of the camera and laser fan-beam projectors.

FIG. 10 shows a laser pattern projected by the structured lightarrangement onto a flat surface S. This pattern, and the patterns ofFIGS. 11 and 12, are ideal patterns that are projected with the deviceperfectly perpendicular to the flat surface S. These patterns areincluded in order to illustrate the working of the device. In practicalsituations, making measurements on the skin surface, more complicatedpatterns will result.

Returning to FIG. 10, the flat surface S is arranged perpendicular tothe camera optical axis and at the crossing point 19 of the three laserfan-beams 20, 21, 22. The crossing point may be at a distance in frontof the device that corresponds to the mid-point of an optimummeasurement range. The optimum measurement range may lie between optimummeasurement limits, with the crossing point 19 at or near to themid-point of those limits. The optimum measurement range may be a rangein which acceptable focus and/or exposure are expected to be obtained.This will depend on the camera used.

This relationship between the crossing point 19 and the optimummeasurement range provides convenient and intuitive user-positioning ofthe device 1. A user may simply position the device such that thecrossing point 19 falls on the skin surface. In this embodiment the useris enabled, or guided, to align the device such that a predeterminedpattern in the form of three stripes crossing at a point is seen on theskin. The user then knows that the device is at or near an optimummeasurement distance, or within an optimum measurement range. There isno need for the user to look at some other alignment device such as adisplay screen on an attached computer. Alignment is possible using thelight pattern itself.

In one embodiment the laser fan-beams are also arranged to mark out animage capture region. In FIG. 10 the laser fan-beams 20, 21, 22 havelengths such that their end points mark out a region indicated by dashedrectangle 24. Dashed rectangle 25 corresponds to the camera field ofview. Dashed rectangles 24, 25 are not projected onto the surface, butare shown in the drawings to illustrate the working of the invention.

The position of the ends of the laser lines on the surface is governedby the laser fan-beam angles subtended by the lines and the distancebetween the device and the surface. The laser line position also dependson the angle of the fan-beam with respect to the optical axis.

This feature provides convenient and intuitive framing. A user can alignthe device such that the laser fan-beams 20, 21, 22 define a region 24that includes a skin feature. Desirably the region will include somehealthy skin around the skin feature. As this region 24 corresponds tothe camera field of view 25, the images captured by the camera will beappropriately framed. Note that no viewfinder or display is required,and indeed in preferred embodiments the device is display-less. This hasa number of advantages. A display-less device has a lower cost and lowerpower consumption than a device with a display.

Further, when measuring skin features in awkward places (e.g. on theunderside of a leg that is being held up by the patient or an assistant)a display on the device is not always visible. However, the skin featureitself is usually visible. In some embodiments a remote display,connected by a wired or wireless connection, may be used. However, inpreferred embodiments the device does not include a display, but usesthe structured light elements themselves to assist in framing, forexample as described above.

Preferably the region 24 is defined by the ends of the laser fan-beams,which span the region 24, passing through the inner part of region 24.This provides framing as discussed above, but also provides goodsampling of structured light data from a central part of the imageframe.

The region 24 preferably defines an area that corresponds to the cameraframe area plus or minus 20%, more preferably plus or minus 15%. As thefan-beam is projected with a fan-beam angle ∝ (FIG. 9), this framing canbe used over various ranges from the device to the skin surface. Thecorrespondence of the region 24 to the frame 25 may vary with rangewhile remaining within the above limits.

While the device may be positioned with the crossing point at the skinsurface, as shown in FIG. 10, the device may also be used at otherranges. FIG. 11 shows the laser pattern on a flat surface S when thedevice is positioned closer to the surface S than in the position ofFIG. 10. Here the three laser fan-beams 20, 21, 22 form an equilateraltriangle and may extend beyond the triangle to define the region 24.

FIG. 12 shows the laser pattern on a flat surface S when the device ispositioned further away from the surface S than in the position of FIG.10. Here the three laser fan-beams 20, 21, 22 also form an equilateraltriangle and may extend beyond the triangle to define the region 24. Thetriangle of FIG. 12 is inverted when compared to the triangle of FIG.11.

FIG. 13 shows the laser pattern that may be projected onto a skinsurface. In this example a patient has an ulcer or other wound W on hisor her leg L. The leg L has a natural curvature from a high point alongthe centre and falling away towards the top and bottom of the imageframe 25.

In addition, in this example the wound W is recessed in the skinsurface. This is typical of ulcers, for example.

The laser fan-beam pattern reflects this more complex shape. Outside ofthe wound W the laser fan-beams form generally smooth curves. Thesecurves contain data that reflect the overall shape of the patient's legL.

Inside the wound W the laser-fan-beams will have a different curvature.Inside the wound W, the curves contain data that reflect the shape ofthe wound.

From the structured light data obtained from the three laser fan-beams,together with information about the wound boundary, it is possible toestablish a model of the surface of the wound W and/or to obtaininformation such as a wound area, wound depth or wound volume. Variousmodeling techniques and measurements are discussed in the Applicant'scopending application published as US2009/213213, the contents of whichare hereby incorporated by reference herein. A model of the leg surface,or other anatomical surface as appropriate, may also be established ifdesired.

The device 1 captures image data using the camera 5. One example of acapture sequence will now be described with reference to FIG. 17. Othersequences may also be suitable.

In a first step 60 a first image is captured without any laser fan-beamsbeing switched on. This is an image of the skin surface and skin feature(e.g. wound, lesion, mole etc). Optionally this image capture may bepreceded by one or more calibration images 61 designed to ensure thatthe first image is captured with acceptable exposure. The first imagemay be captured with illumination from the light sources 11, andexposure may be adjusted in the camera 5 or by adjusting the poweroutput of the light sources 11. Alternatively the first image and itsassociated calibration images, if any, may be captured at a later pointin the capture sequence.

In a second step 62 an image is captured with all three laser fan-beamsturned on. This structured light image can be processed to obtain thestructured light data allowing measurements to be made on the skinfeature.

It is not always possible to differentiate unambiguously between thelaser fan-beams in the structured light image. This may lead to errorsor inaccuracies in any measurements that may be made. In order toaddress this problem, one or more disambiguation images may also becaptured at step 63. Preferably n−1 disambiguation images are captured,where n is the number of laser fan-beams used. Each image is capturedwith a subset of the laser fan-beams turned on. For example, eachdisambiguation image may include a single laser fan-beam. The data fromthe disambiguation images can then be used to identify the differentlaser fan-beams unambiguously in the structured light image.

As an alternative, a number of structured light images may be captured,each with just one laser fan-beam switched on. This avoids the need fordisambiguation images, but could allow mis-registration due to movementbetween the structured light images.

The structured light images and/or disambiguation images may also bepreceded by calibration images at step 64 to ensure correct exposure.

Preferably the images are captured over a very short space of time. Thisprevents significant movement between the images. In one embodiment,calibration images, the first image, structured light image anddisambiguation images may all be captured in less than 1 second,preferably around 0.1-0.5 seconds. Memory, in particular a buffer, maybe provided in the device 1 to allow rapid capture of image data. Datamay be transferred at a slower rate from the handheld device 1 to anexternal device.

All images are preferably captured in response to a singleuser-actuation of the capture switch or button 4.

Thus, in use the device 1 may be directed by a user so that optical axis7 is approximately aligned with the central region of wound W. The usermay use the projected laser stripes to assist in framing, as discussedabove. The laser fan-beams or stripes 20, 21, 22 are projected acrosswound W and the image or images are captured by camera 5. The skilledreader will understand that, due to the fixed angular relationship ofthe laser fan beams 20, 21, 22 and the optical axis 7 that the threedimensional positions of points along the laser fan beams may bedetermined from the structured light data. Models of the wound surfaceand the skin surface may then be developed to fit the three dimensionalposition data obtained.

The wound surface model and/or skin surface model may be an inelasticsurface draped between the three-dimensional coordinates of thestructured light elements, or an elastic surface stretched between thethree-dimensional coordinates, or a model of the anatomy, or simply ascaled planar projection. A model of the anatomy may be a modelretrieved from a library of models, or simply a geometric shapeapproximating anatomy (a cylinder approximating a leg, for example).

FIG. 15 shows a laser pattern projected onto a surface by a device thatis a modification of the device of FIG. 1. This device projects two setsof laser beams. In FIG. 15 one set of laser fan-beams 50, 51, 52 isshown in solid line, while a second set of laser fan-beams 54, 55, 56 isshown in dashed line. This is solely for the purposes of clarity. Inpractice the laser fan-beams may all be the same, or each set may be adifferent color or frequency.

In the embodiment of FIG. 15, the lasers are arranged such that acrossing point of the first set of laser fan-beams is a first distancefrom the device, and a crossing point of the second set of laserfan-beams is a second distance from the device. The first distance maycorrespond to a minimum measurement distance and the second distance toa maximum measurement distance (or the first and second distances arethe limits of an optimum measurement range). A user adjusts the distancebetween the device and the skin such that the skin surface falls betweenthe two crossing points.

Further, the position of the skin surface within the optimum measurementrange may be apparent from the laser pattern. In FIG. 15 two trianglesare defined by the two sets of laser fan-beams 50, 51, 52 and 54, 55,56. If the device has two sets of laser projectors mounted together(i.e. two laser projectors at each point 9 in FIG. 7), then thetriangles will be inverted with respect to each other (as is the case inFIG. 15) within the optimum measurement range. This is because of theinversion of each triangle with distance, as discussed above withreference to FIGS. 11 and 12. If the triangles are not inverted withrespect to each other, then the skin surface is either closer than thenearer crossing point, or more distant than the further crossing point.In other words, when the user sees a predetermined pattern in the formof two triangles inverted with respect to each other, they know that thedevice is within the optimum measurement range.

In a further embodiment shown in FIG. 16, two sets of laser fan-beamprojectors are offset, with a first set of projectors 9 positioned as inFIG. 7 and a second set of projectors 9′ positioned in-between theprojectors 9. In the embodiment of FIG. 16, each set is a set of threelaser fan-beam projectors and the lasers are arranged such that acrossing point of the first set of laser fan-beams is a first distancefrom the device, and a crossing point of the second set of laserfan-beams is a second distance from the device. The first distance maycorrespond to a minimum measurement distance and the second distance toa maximum measurement distance (or the first and second distances arethe limits of an optimum measurement range).

In this embodiment the triangles will be inverted when the skin surfaceis outside of the optimum measurement range. If the shapes of the twotriangles are the same (i.e. not inverted) then the skin surface iswithin the optimum measurement range. In other words, when the user seesa predetermined pattern in the form of two triangles with the sameorientation, they know that the device is within the optimum measurementrange.

In another embodiment shown in FIG. 18, a single set of three laserfan-beam projectors is provided, with the beams again arranged to crossin front of the device. In this embodiment the fan-beam angle ∝ and theangle with respect to the optical axis 7 are such that the three laserstripes cross at a crossing point 19 at an optimum measurement range. Atother ranges the lines will form triangles. Further, the laser stripesof this embodiment may be projected together with small markers 80, suchas laser spots or some other identifiable feature, such as dots, smalllines crossing the laser stripe, small gaps in the laser stripe etc. Thefan-beam angle and angle to the optical axis may be arranged such thatwhen the markers 80 on different laser stripes align with each other,the device is at the outer limit of the optimum measurement range. Thus,FIG. 19 shows the laser pattern at the lower limit of the optimummeasurement range, while FIG. 20 shows the laser pattern at an upperlimit of the optimum measurement range. In this embodiment, when theuser sees a predetermined pattern in the form of the lines crossing at acrossing point (as in FIG. 18) the user will know that the device is ator near an optimum measurement distance from the skin surface; or if theuser sees a predetermined pattern in the form of a triangle, withmarkers 80 positioned outside the corners of the triangle the user willknow that the device is within an optimum measurement range. If themarkers 80 are inside the corners of the triangle then the device isoutside the optimum measurement range. As with other embodiments, theequilateral triangle pattern is shown for illustrative purposes andcorresponds to projection onto a flat surface perpendicular to theoptical axis. More complex patterns result from projection onto morecomplex surfaces.

FIG. 14 shows the device 1 that may form part of a broader system 30.The device 1 includes a controller 31 that controls the camera 5,structured light projectors 9 and the light sources 11 (not shown inFIG. 14). The controller 31 is configured to control these components inresponse to user-actuation of the capture switch 4. The data generatedby these devices is passed to a buffer memory 32, which holds the datauntil it can be passed from the device to an external computer 33.

The device 1 may be connected to the external computer by any suitablemechanism. Wired connections, such as USB or Firewire connections, maybe used. The device may be configured to dock in a physical dockconnected to the external computer 33. Alternatively, wirelessconnections may be used, including e.g. Bluetooth.

In any case, the device 1 includes a communications port 35 arranged forwired or wireless communications. In the embodiment shown in FIGS. 1 to7 the communications port 35 is a USB port. Data is transmitted from thecommunications port 35 to the external computer 33.

The external computer 33 includes a processor 37 and memory 38. Theexternal computer may also include a display 39 and output devices suchas printers 40 and the like. The external computer 33 may include userinput devices such as keyboard 41 and mouse 42. A stylus 43 may also beprovided. The external computer 33 may be connected to a database 44.

The external computer may be any suitable computer or collection ofcomputer devices, including: PDAs, Smartphones, Personal Computers,Laptops, Tablet computers etc.

Thus the device 1 is configured to capture data and transmit that datato the external computer 33. In one embodiment the device 1 does notperform any processing of the data, but simply passes it to the externalcomputer 33. The device 1 preferably has no display. A user may capturedata using the device 1 but analyses the data using the externalcomputer 33.

Desirably a user may be permitted to manually define a skin featureboundary. This may be done using a mouse 42 or other pointing device, orthe stylus 43. The boundary may be used to assist in developing a modelof the wound surface and/or in determination of wound depth, area and/orvolume. Utilizing manual input of the outline avoids the need forcomplex image processing capabilities. Further, this approach utilizeshuman image processing capabilities to determine the outline whereautomated approaches may be less effective.

Data may be maintained in the database 44 and used for monitoring of theskin feature over time. For example, records gathered over a time periodcan be used to monitor the healing of a wound or ulcer, or the growth ofa potentially cancerous mole. Alerts may be generated if healing orgrowth exceeds a threshold.

The external computer may communicate with a central server thatmaintains the database 44. In this way data captured by a number ofdevices 1 may be centrally stored in a convenient manner.

This centralized system allows appropriate categorizing and storage ofdata for future use. For example, by mining historical data from thedatabase it is possible to analyze the efficacy of a particulartreatment or to compare different treatments. Statistical trends ofconditions, treatments and outcomes can be monitored. This data can beused to suggest a particular treatment, based on a set of symptomsexhibited by a particular patient. Data can provide predictions forwound healing. Where actual healing differs from the prediction by morethan a threshold, the system may issue an alert.

A healthcare provider may use the data to audit efficiency of its wholeorganization, departments within the organization or even individualworkers. Historical data may be compared with historical workerschedules to determine whether workers are performing all tasks on theirschedules. Efficiencies of different workers may be compared.

Data may be stored in a patient record along with measurementinformation (wound area, wound depth, wound volume etc). Where previousinformation has been stored comparative measurements may be made and anindication of improvement or deterioration may be provided. Data may besent directly to a central database or distributed to medicalprofessionals for evaluation. This allows an expert to reviewinformation obtained in the field and provide medical direction whilethe health practitioner is visiting the patient. The historic recordallows patient progress to be tracked and re-evaluated, if necessary.

Measurements of other wound information may also be made. The color ofthe wound and the size (linear dimension, area or volume) of particularcolored regions may also be calculated. These measurements may require acolor reference target to be placed within the image capture area foraccurate color comparison to be made.

There are thus provided methods of measuring wounds that are simple,inexpensive, repeatable and may be performed remotely, withoutcontacting the skin surface. The methods may utilize human imageprocessing capabilities to minimize the processing requirements. Themethods do not require the placement of articles near the wound. Themethods allow historical comparison of a wound. The device 1 is portablewith relatively low processing requirements and enables records to besent wirelessly or over a wired connection for evaluation and storage.

Further devices, such as GPS units, auxiliary sensors, temperaturesensors, pH sensors, moisture sensors, odor sensors, optical probes,fluorescence probes and/or Doppler ultrasound probes, may be used incombination with the device 1, as discussed in the Applicant's copendingapplication published as US2009/213213.

While the present invention has been illustrated by the description ofthe embodiments thereof, and while the embodiments have been describedin detail, it is not the intention of the Applicant to restrict or inany way limit the scope of the appended claims to such detail.Additional advantages and modifications will readily appear to thoseskilled in the art. Therefore, the invention in its broader aspects isnot limited to the specific details, representative apparatus andmethod, and illustrative examples shown and described. Accordingly,departures may be made from such details without departure from thespirit or scope of the Applicant's general inventive concept.

The invention claimed is:
 1. A handheld skin monitoring or measuringdevice, including: a camera having a camera optical axis; and astructured light arrangement configured to project three or more laserfan beams such that the laser fan beams cross at a crossing point infront of the camera and a user is enabled to position the handheld skinmonitoring or measuring device at a distance from a skin surface withinan optimum range without reference to a display by aligning the crossingpoint of the laser fan beams with the skin surface.
 2. A handheld skinmonitoring or measuring device as claimed in claim 1 wherein thestructured light arrangement is configured to project the laserfan-beams such that a pattern formed by the laser fan beams on a skinsurface varies with a distance between the device and the skin surface,and wherein the pattern is a predetermined pattern when the device is ata distance from the skin surface within an optimum range, such that auser is enabled to position the handheld skin monitoring or measuringdevice at a distance from the skin surface within the optimum range byadjusting the distance such that the predetermined laser pattern isformed on the surface.
 3. A handheld skin monitoring or measuring deviceas claimed in claim 1 further including a capture switch, the devicebeing arranged to capture data on actuation of the capture switch.
 4. Ahandheld skin monitoring or measuring device as claimed in claim 1further including a communications port, the device being configured totransmit data captured by the camera from the communications port.
 5. Ahandheld skin monitoring or measuring device as claimed in claim 1further including memory configured to store data captured by thecamera.
 6. A handheld skin monitoring or measuring device as claimed inclaim 1, further including one or more light sources configured toilluminate the skin surface.
 7. A handheld skin monitoring or measuringdevice as claimed in claim 1, configured to capture at least thefollowing data in response to a single user capture instruction: animage with the laser fan beams switched off; and at least three imageseach including one or more laser fan beams, such that each laser fanbeam is unambiguously identifiable.
 8. A handheld skin monitoring ormeasuring device as claimed in claim 1, further including asubstantially spherical housing dimensioned to fit a user's cupped hand,the camera and structured light arrangement being mounted in thehousing.
 9. A handheld skin monitoring or measuring device as claimed inclaim 1, wherein the structured light arrangement is configured toproject three laser fan beams from sources distributed evenly around thecamera optical axis such that the three laser fan beams form asubstantially equilateral triangle in any plane that is perpendicular tothe camera optical axis and does not include the crossing point.
 10. Ahandheld skin monitoring or measuring device as claimed in claim 1,wherein the structured light arrangement is configured to project threelaser fan beams.
 11. A handheld skin monitoring or measuring device,including: a camera having a camera optical axis; and a structured lightarrangement configured to project three or more laser fan beams suchthat the laser fan beams cross at a crossing point in front of thecamera, wherein the camera has a camera field of view and the three ormore laser fan beams subtend fan beam angles corresponding to the camerafield of view, such that the ends of the laser beams projected onto askin surface define a region that substantially corresponds to an imageframe of the camera.
 12. A handheld skin monitoring or measuring deviceas claimed in claim 11 wherein the region occupies between 80% and 120%of the area of the image frame.
 13. A handheld skin monitoring ormeasuring device, including: a camera having a camera optical axis and acamera field of view; and a structured light arrangement configured toproject three or more laser fan beams such that the laser fan beamscross at a crossing point in front of the camera, the laser fan beamssubtending fan beam angles corresponding to the camera field of view,such that the ends of the laser beams projected onto a skin surfacedefine a region that substantially corresponds to an image frame of thecamera.
 14. A handheld skin monitoring or measuring device as claimed inclaim 13 wherein the region occupies between 80% and 120% of the area ofthe image frame.
 15. A handheld skin monitoring or measuring device asclaimed in claim 13, wherein the structured light arrangement isconfigured to project three laser fan beams from sources distributedevenly around the camera optical axis such that the three laser fanbeams form a substantially equilateral triangle in any plane that isperpendicular to the camera optical axis and does not include thecrossing point.
 16. A method of capturing data concerning a skin featureusing a handheld skin monitoring or measuring device, including: acamera having a camera optical axis and a camera field of view; astructured light arrangement configured to project three or more laserfan beams such that the laser fan beams cross at a crossing point infront of the camera; the laser fan beams subtending fan beam anglescorresponding to the camera field of view, such that the laser beamsprojected onto a skin surface define a region that substantiallycorresponds to an image frame of the camera; the method including:directing the handheld skin monitoring or measuring device towards askin surface; projecting at least some of the laser fan beams using thestructured light arrangement; and adjusting a position of the handheldskin monitoring or measuring device such that laser fan beams define adesired image region on the skin surface; and capturing data using thecamera.
 17. A display-less handheld skin monitoring or measuring deviceincluding: a substantially spherical housing dimensioned to fit thecupped hand of a user; a camera mounted in the housing; a structuredlight arrangement mounted in the housing and configured to project threeor more laser fan beams such that the laser fan beams cross at acrossing point in front of the camera; and a communications linkconfigured to transmit image data captured by the camera.
 18. Adisplay-less handheld skin monitoring or measuring device as claimed inclaim 17, including a capture button positioned on the substantiallyspherical housing such that, in use, the capture button is accessible toone of the user's fingers or thumb.